2. See the notches? They tell you where you'll have to match up the fabrics. To sew together two ACs align the edges of the concave curve right side up and the convex curve of the other AC wrong side up on top and begin sewing with a 1/4" seam allowance.

9. Because the seam allowances were pressed toward the concave curve, they nest perfectly. Again, no need to pin, just align the intersection. Of course, now it's impossible that only one curve is on the bottom!